1. Field of the Invention
The present invention relates to improvements in an installation for measuring an instantaneous flying position of a spherical object, and a method for measuring launch angles thereof.
2. Description of the Related Art
In order to measure an instantaneous spatial position, a vertical launch angle, or a lateral deviation angle (a horizontal launch angle) of a spherical flying object such as a golf ball, a tennis ball or the like, the following conventional methods (i), (ii), (iii) and (iv) are employed.
(i) A great number of electric codes connected to electric switches are located along an expected flight path of a spherical object. In this method, the spherical object is caused to impinge on a particular one of the codes, to thereby actuate a corresponding one of the electric switches.
(ii) A great number of transmission type or reflection type photoelectric switches are placed along an expected flight path of a spherical object, and a particular one of the photoelectric switches is actuated when a ray input for that particular switch is blocked off by the spherical object in flight.
(iii) Scanning laser beams are created, and are paralleled across an expected flight path of a spherical object by using a combination of a concave mirror with a lens system. The spherical object is made to pass through the scanning plane, to thereby measure beam cut-off timing to determine an instantaneous spatial position and launch angles of the spherical object in flight.
(iv) An image of a spherical object in flight is taken by using a video camera. An instantaneous spatial position, a vertical launch angle, or a horizontal launch angle (lateral deviation angle) of the spherical object is determined by means of image measurement.
In the foregoing first method (i), however, the contact of the spherical object in flight with each electric code affects the flight of the spherical object, and for this reason, the first method (i) is not desirable.
The second method (ii) is disadvantageous in that a great number of photoelectric switches are required to be provided in order to optically cover a wide flight path area of the spherical object and to improve the resolution of detection.
In the third method (iii), the concave mirror causes the laser beams to be inevitably irregular in their scanning translational movement owing to their mechanical motions such as their swinging or rotating motions. Moreover, the mechanical movement of the mirror may also affected by atmospheric temperatures and other ambient conditions. This makes errors in the position measurement. This is a disadvantage of the third method (iii).
In the fourth method (iv), the location in which the video camera is placed causes errors in the measurement. Moreover, the number of the pixels or the picture elements of the image, and the lighting of the flying spherical object limit the accuracy in the measurement. This is a problem of the fourth method (iv).
In order to overcome the foregoing disadvantages or problems of the conventional measuring methods, the inventors have intended an apparatus for determining instantaneous spatial position of a flying spherical object according to an invention protected under U.S. Pat. No. 5,160,839 granted to the inventors of the present application. In the apparatus disclosed in U.S. Pat. No. 5,160,839, a parallel light band is generated, and it is projected onto a screen to form a linear image region. If a spherical object in flight crosses the parallel light band, it creates a silhouette on the screen within the image region. The position of this silhouette is detected by using a sensor means, to thereby determine an instantaneous spatial position of the flying spherical object.
However, in this position determining apparatus of U.S. Pat. No. 5,160,839, the computation of the position is based upon a silhouette of a spherical object in flight, which is formed on the screen. Defects in the screen such as a slant warp or contamination, act to reduce the accuracy of the measurement.
It is therefore an object of the present invention to provide for an improved type measuring apparatus in which it is feasible to determine an instantaneous spatial position of a spherical object in flight without coming into contact therewith in a wide flight path area of the spherical object and with higher measuring accuracy.
It is another object of the present invention to provide for a measuring method in which vertical or horizontal launch angles of a flying spherical object can be measured without any contact therewith in a wide flight path area and with higher measuring accuracy.